Selective reception of alternating currents



E. E. PERNOT AND L. J. RICH.

SELECTIVE RECEPTION 0F ALTERNATING CURR ENTSL APPuqAnou HLED MAR 30. 1922 1,426,334. Patented Aug. 15, 1922.

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F. E. PERNOT AND L. J. RICH. SELECTIVE RECEPTION 0F ALTERNATING CURRENTS.

APPLICATION FlLED MAR. 30, 1922. PatentedAug 1922. 0 2 S.HETSSHEET 2.

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To all whom it may concern:

Be it known that we, FREDERICK E. PER- NOT and LESTER J. RIoH, citizens of the United States, and residents, respectively, of Washington, D. (3., have invented certam new and useful Improvements in Selective Reception of Alternatin Currents, of which the following is a speci cation.

The present invention has reference to irn provements in a novel method for the electrical transmission of signals, having for an object to provide a method whereby to effect the separation of currents differing in frequency from one another, as well as for the combination, without mutual interaction of currents of different frequencies.

In order that the invention and its mode of application may be readily understood by workers skilled in the art, we have in the accompanying. illustrative drawings and in the detailed following description based thereon, set out practlcal embodiments of the invention.

In these drawings:

Figure 1 is a schematic view of one form of apparatusfor separating currents of different frequencies;

Figure 2 is a modified form thereof;

Figure 3 is a similar view showing another modified form;

Figure 4: is a. like view illustrating a still further modified means for separating cur-' rents of different frequencies;

Figure 5 is a schematic view of yet another modified form of the invention; and,

Figure 6 is a schematic view of a still further modification of our invention.

Having more particular reference to the drawings, in connection with which like reference characters will designate corresponding parts throughout the several views, prefatorily, the separation of current of one particular frequency is accomplished by elimination, one by one or sequentially, of the currents of all other frequencies which may be present. The elimination of any frequency is accomplished by the adjustment of a network of impedances, a sin le unit of such an arrangement or network eing represented in Figure 1.

In Figural, O and 0' indicate conductors for bringing in currents of different freuencies, one of which is to be suppressed by t at portion of the network or the unit illustrated in the figure, while the currents of Specification of Letters Patent. Patented Aug, 15, 1922,

Application filed March 30, 1922. Serial No. 548,254.

nated at Z Z Z and Z in form of a l/Vheatstone bridge or provided, the same being made of combinations of resistance, inductance, and capacity, either in series or in parallel. By adjusting the values of these impedances so that for the frequency which it is desired to eliminate Z,Z,=Z Z no current ofthis particular frequency can. flow from the mesh 0 and 0 into mesh 1 and 1. If the impedances are further selected so that the relation expressed bythe above equation does not hold for any other frequency, currents of all other frequencies will pass from mesh 0 and O to mesh 1 and 1 An alternative method of suppressing a single frequency is shown in Figure 2 where in O and Oare conductors for bringing in currents of several different frequencies, one of which is to be suppressed, while the others pass on through conductors 1 and 1. A condenser C is arranged in this particular form, while inductances L and L are also provided, there being a mutual inductance M between L and L. Thus, if one of these frequencies is to be suppressed, such frequency being herein indicated for convenience by the letter 7, this will be accomplished when M and C are so adjusted that the relation expressed by the following equation holds good.

power loss in the condenser C.-

The forms of invention hereinbefore described have been set up as unit systems for the elimination of one particular frequency and are well known .in the art of electrical measurements, their application having been mainly to a comparison of the physical properties of the component parts of the network. The novelty of the present invention may be stated to reside in the use of systems of this character for the separation of currents of different frequencies used in the alternating current multiplex systems of signal transmission and in the manner of combination of individual units. The terminals of the unit systems previously described are conjugate and therefore, the action as set forth, takes place regardless of the direction of transmission of energy through the unit system; that is, for any such unit system there is a particular frequency which it cannot transmit in either direction, while transmitting other frequencies independently of the direction.

Toseparate currents of different -frequencies several oi the units as described above must be suitably interconnected. Practical embodiments of the possible methods of interc-onnecting unit systems in order to separate currents of two different frequencies, are illustrated in the Figures l and 5. in Figure l, which may be termed the preferred form of connection for separating only two frequencies, indicated in the figures by f and 72, the two unit systems, such as illustrate. in Figure 1, are connected in parallel at one oi their terminals and "from this parallel connection go the conductors (l and 0, which constitute any desired pon tion of the complete system designated to carry currents of two frequencies. The other terminals 1 and 1 and 2 and 2" of the unit systems are reserved for connection to that portion of the apparatus from which is desired to exclude all currents except those of a single frequency. Network indi-- cated at Z Z Z5, and if is arranged as described in connection with the equation first noted in this specification in connection with the Figure 1 to suppress currents or frequency i, so that currents of frequency 7, produced anywhere else in the entire system cannot appear at terminals 1 and 1. Similarly, network Z Z Z and Z, is arranged so that the frequency f, is suppressed and therefore, no currents of this 'irequency produced anywhere else in the system can appear at the terminals 2 and 2'.

In the Figure 5 we have shown another method of connecting the two unit systems, such as shown in the Figure 2 to accomplish these results as set up in connection with the ligure t. The terminals of this systern which are to be acted upon by the currents of both f equencies, are connected in series, instead or in parallel, as is done in. the Figure The that in Figure ti a different lrind or unit system from own in at is used, has no ing "upon the manner in whic termiare connected, here, it may be notes that in this particular figure, L and indicate the inductances between which there a mutua inductance M, while C designates incense the condensers used in connection with these several units. 1

In the Figure 6, a still further arrangement is illustrated and is capable of being employed when a greater number of frequencies are to be separated. In this particular form, four frequencies are separated. At the terminals 0 and O, currents of four different frequencies may be theterminals land 1', 2 and 2, 3 and 3, and 4 and 4', currents of any one of the four frequencies indicated adjacent the terminals Q and O by f f f and 7", will be present. Assuming for the sake of clarity, the currents of four frequencies, f,, f,, and f enter at the terminals 0 and the operation of the apparatus will be as tollows :-;lhe four frequencies enter unit system A where f, is suppressed, leaving the frequencies f f and f, to pass on into the unit system B, whereat the frequency f is suppressed. The remaining frequencies f and f, are separated by the unit systems C and D as described in connection with the Figures l or 5, so that finally, at terminals 1 and 1', only the frequency f, is present and at the terminals 2 and 2 only the frequency f, appears. The unit systems E and F suppress frequencies f, and f, in the same man- 'ner as systems A and B suppress frequencies 7, and 1. Systems G and H separate frequencies f, and f, so that f, appears at terminals 3 and 3' and the frequency f, appears at terminals a and l. As in the case of Figure 5, the first systems A and E may be connected in series instead of in parallel as shown, as is also true with systems (3 and l) and systems G and H.

Although we have hereinbefore described. our apparatus as only separating currents of different frequencies entering at terminals U and O, it is to be fully understood that it serves also as a means for combining ourpresent, While at rents of different frequencies when they are impressed at the terminals 1 and 1', 2 and 2, 8 and 3, and l and a, the manner of the combination being such that the current impressed at any one pair of terminals does not appear at any other pair except- U and t). [is illustrating the action of the several systems, consider current of frequency f, to be supplied to terminals 2 and 2. l fith the systems adjusted as hereinbefore described, the current can pass "from 2 and 2 to U and U, for neither A, B, nor l) is adjusted to suppress this frequency. They cannot appear at 1 and 1 because C is adjusted to suppress this particular frequency. .The current cannot appear at terminals 3 and 3 and l and l because system F is adjusted to suppress this same frequency. The same is true :tor any other one oi the four different frequencies.

separate currents of any number of irequencies, suitable extensions or additions of the systemsherein described are capable of bein successfully employed.

anifestly, the apparatus shown are capable of considerable modification and such modification as is Within the scope of our claim, we consider Within the spirit of our invention.

We claim- A system for the selective transmission of a plurality of currents of. different frequency between a common transmission'circuit, and circuits individual to said fre uencies, comprising a plurality of branc es for said common circuit and sub-branches for each branch, selective suppressing devices for for each frequency a single selective path extending from the common circuit to its in dividual circuit by Way of a branch, a subbranch and seleetive'frequency devices for each of theother frequencies, whereby said other frequencies are individually and successively suppressed.

FREDERICK E; PERNOTL/ LESTER J. RICH. 

